Comprehensive imaging analysis of intracranial atherosclerosis.

Intracranial atherosclerotic disease (ICAD) involves the build-up of atherosclerotic plaques in cerebral arteries, significantly contributing to stroke worldwide. Diagnosing ICAD entails various techniques that measure arterial stenosis severity. Digital subtraction angiography, CT angiography, and magnetic resonance angiography are established methods for assessing stenosis. High-resolution MRI offers additional insights into plaque morphology including plaque burden, hemorrhage, remodeling, and contrast enhancement. These metrics and plaque traits help identify symptomatic plaques. Techniques like transcranial Doppler, CT perfusion, computational fluid dynamics, and quantitative MRA analyze blood flow restrictions due to ICAD. Intravascular ultrasound or optical coherence tomography have a very high spatial resolution and can assess the structure of the arterial wall and the plaque from the lumen of the target vascular territory. Positron emission tomography could further detect inflammation markers. This review aims to provide a comprehensive overview of the spectrum of current modalities for atherosclerotic plaque analysis and risk stratification.

Reactive axillary lymph nodes after COVID-19 mRNA vaccination: comparison of mRNA vs. attenuated whole-virus vaccines.

OBJECTIVE: To compare the incidence and natural course of reactive axillary lymph nodes (RAL) between mRNA and attenuated whole-virus vaccines using Deauville criteria. METHODS: In this multi-institutional PET-CT study comprising multiple vaccine types (Pfizer-BioNTech/Comirnaty, Moderna/Spikevax, Sinovac/CoronaVac and Janssen vaccines), we evaluated the incidence and natural course of RAL in a large cohort of oncological patients utilizing a standardized Deauville scaling system (n=522; 293 Female, Deauville 3-5 positive for RAL). Univariate and multivariate analyses were conducted to evaluate the predictive value of clinical parameters (absolute neutrophil count [ANC], platelets, age, sex, tumor type, and vaccine-to-PET interval) for PET positivity. RESULTS: Pfizer-BioNTech/Comirnaty and Moderna vaccines revealed similar RAL incidences for the first 20 days after the second dose of vaccine administration (44% for the first 10 days for both groups, 26% vs. 20% for 10-20 days, respectively for Moderna and Pfizer). However, Moderna recipients revealed significantly higher incidences of RAL after 20 days compared to Pfizer-BioNTech/Comirnaty, with nodal reactivity spanning up to the 9th week post-vaccination (15% vs. 4%, respectively P  < 0.001). No RAL was observed in patients who received either a single dose of J&J vaccine or two doses of CroronaVac. Younger patients showed increased likelihood of RAL, otherwise, clinical/demographic parameters were not predictive of RAL ( P  = 0.014 for age, P  > 0.05 for additional clinical/demographic parameters). CONCLUSION: RAL based on strict PET criteria was observed with mRNA but not with attenuated whole-virus vaccines, in line with higher immunogenicity and stronger protection offered by mRNA vaccines.

Delayed Enhancement of Intracranial Atherosclerotic Plaque Can Better Differentiate Culprit Lesions: A Multiphase Contrast-Enhanced Vessel Wall MRI Study.

BACKGROUND AND PURPOSE: Intracranial plaque enhancement (IPE) identified by contrast-enhanced vessel wall MR imaging (VW-MR imaging) is an emerging marker of plaque instability related to stroke risk, but there was no standardized timing for postcontrast acquisition. We aim to explore the optimal postcontrast timing by using multiphase contrast-enhanced VW-MR imaging and to test its performance in differentiating culprit and nonculprit lesions. MATERIALS AND METHODS: Patients with acute ischemic stroke due to intracranial plaque were prospectively recruited to undergo VW-MR imaging with 1 precontrast phase and 4 consecutive postcontrast phases (9 minutes and 13 seconds for each phase). The signal intensity (SI) values of the CSF and intracranial plaque were measured on 1 precontrast and 4 postcontrast phases to determine the intracranial plaque enhancement index (PEI). The dynamic changes of the PEI were compared between culprit and nonculprit plaques on the postcontrast acquisitions. RESULTS: Thirty patients with acute stroke (aged 59 ± 10 years, 18 [60%] men) with 113 intracranial plaques were included. The average PEI of all intracranial plaques significantly increased (up to 14%) over the 4 phases. There was significantly increased PEI over the 4 phases for culprit plaques (an average increase of 23%), but this was not observed for nonculprit plaques. For differentiating culprit and nonculprit plaques, we observed that the performance of IPE in the second postcontrast phase (cutoff = 0.83, AUC = 0.829 [0.746-0.893]) exhibited superior accuracy when compared with PEI in the first postcontrast phase (cutoff = 0.48; AUC = 0.768 [0.680-0.843]) (P = .022). CONCLUSIONS: A 9-minute delay of postcontrast acquisition can maximize plaque enhancement and better differentiate between culprit and nonculprit plaques. In addition, culprit and nonculprit plaques have different enhancement temporal patterns, which should be evaluated in future studies.

Comparison of brain imaging and physical health between research and clinical neuroimaging cohorts of ageing.

OBJECTIVES: To compare brain MRI measures between Adult Changes in Thought (ACT) participants who underwent research, clinical, or both MRI scans, and clinical health measures across the groups and non-MRI subjects. METHODS: Retrospective cohort study leveraging MRI, clinical, demographic, and medication data from ACT. Three neuroradiologists reviewed MRI scans using NIH Neuroimaging Common Data Elements (CDEs). Total brain and white matter hyperintensity (WMH) volumes, clinical characteristics, and outcome measures of brain and overall health were compared between groups. 1166 MRIs were included (77 research, 1043 clinical, and 46 both) and an additional 3146 participants with no MRI were compared. RESULTS: Compared to the group with research MRI only, the clinical MRI group had higher prevalence of the following: acute infarcts, chronic haematoma, subarachnoid haemorrhage, subdural haemorrhage, haemorrhagic transformation, and hydrocephalus (each P < .001). Quantitative WMH burden was significantly lower (P < .001) and total brain volume significantly higher (P < .001) in research MRI participants compared to other MRI groups. Prevalence of hypertension, self-reported cerebrovascular disease, congestive heart failure, dementia, and recent hospitalization (all P < .001) and diabetes (P = .002) differed significantly across groups, with smaller proportions in the research MRI group. CONCLUSION: In ageing populations, significant differences were observed in MRI metrics between research MRI and clinical MRI groups, and clinical health metric differences between research MRI, clinical MRI, and no-MRI groups. ADVANCES IN KNOWLEDGE: This questions whether research cohorts can adequately represent the greater ageing population undergoing imaging. These findings may also be useful to radiologists when interpreting neuroimaging of ageing.

Intracranial aneurysm wall displacement depicted by amplified Flow predicts growth.

BACKGROUND: Abnormal intracranial aneurysm (IA) wall motion has been associated with IA growth and rupture. Recently, a new image processing algorithm called amplified Flow (aFlow) has been used to successfully track IA wall motion by combining the amplification of cine and four-dimensional (4D) Flow MRI. We sought to apply aFlow to assess wall motion as a potential marker of IA growth in a paired-wise analysis of patients with growing versus stable aneurysms. METHODS: In this retrospective case-control study, 10 patients with growing IAs and a matched cohort of 10 patients with stable IAs who had baseline 4D Flow MRI were included. The aFlow was used to amplify and extract IA wall displacements from 4D Flow MRI. The associations of aFlow parameters with commonly used risk factors and morphometric features were assessed using paired-wise univariate and multivariate analyses. RESULTS: aFlow quantitative results showed significantly (P=0.035) higher wall motion displacement depicted by mean±SD 90th% values of 2.34±0.72 in growing IAs versus 1.39±0.58 in stable IAs with an area under the curve of 0.85. There was also significantly (P<0.05) higher variability of wall deformation across IA geometry in growing versus stable IAs depicted by the dispersion variables including 121-150% larger standard deviation ([Formula: see text]) and 128-161% wider interquartile range [Formula: see text]. CONCLUSIONS: aFlow-derived quantitative assessment of IA wall motion showed greater wall motion and higher variability of wall deformation in growing versus stable IAs.

Risk of unruptured aneurysms in subarachnoid hemorrhage patients with multiple intracranial aneurysms: a multicenter, longitudinal, comparative study from China.

BACKGROUND: In aneurysmal subarachnoid hemorrhage patients with multiple intracranial aneurysms (aSAH-MIA patients), the risk of secondary unruptured intracranial aneurysms is inconsistent. This study aimed to explore the risk of unruptured aneurysms in Chinese aSAH-MIA patients. METHODS: The medical records and angiographic images of aSAH-MIA patients from eight cerebrovascular centers in China were retrospectively reviewed and analyzed. Patients with a single unruptured intracranial aneurysm (UIA) and no prior aSAH were used as controls. Propensity score matching (PSM) was employed to balance the differences in age, gender, aneurysm size, aneurysm site, and follow-up duration between the two groups. RESULTS: The study included 267 unruptured aneurysms from 204 aSAH-MIA patients and 769 single UIA. After PSM, 201 aneurysms were enrolled in the aSAH-MIA group and 201 aneurysms in the control group. The mean follow-up was 2.2 years. Thirty-four aneurysm instability events (28 growth and 6 rupture, 16.9%) occurred during follow-up in the aSAH-MIA group and 16 instability events (13 growth and 3 rupture, 8%) occurred in the control group. Risk factors for aneurysmal instability were aneurysm irregularity (OR 2.53; 95% CI 1.18 to 4.31), higher size ratio (OR 1.23; 95% CI 1.37 to 4.39), and middle cerebral artery location (OR 1.86; 95% CI 1.03 to 3.17). The risk of aneurysmal instability was substantially elevated in the aSAH-MIA group (HR 2.07; 95% CI 1.12 to 3.02). CONCLUSIONS: Unruptured aneurysms in Chinese aSAH-MIA patients exhibited higher risks of growth and rupture than in patients with a single UIA. Middle cerebral artery location, higher size ratio and irregular shape were associated with higher risk of growth or rupture.

Wall permeability on magnetic resonance imaging is associated with intracranial aneurysm symptoms and wall enhancement.

OBJECTIVES: Wall remodeling and inflammation accompany symptomatic unruptured intracranial aneurysms (UIAs). The volume transfer constant (Ktrans) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) reflects UIA wall permeability. Aneurysmal wall enhancement (AWE) on vessel wall MRI (VWI) is associated with inflammation. We hypothesized that Ktrans is related to symptomatic UIAs and AWE. METHODS: Consecutive patients with UIAs were prospectively recruited for 3-T DCE-MRI and VWI from January 2018 to March 2023. UIAs were classified as asymptomatic and symptomatic if associated with sentinel headache or oculomotor nerve palsy. Ktrans and AWE were assessed on DCE-MRI and VWI, respectively. AWE was evaluated using the AWE pattern and wall enhancement index (WEI). Spearman's correlation coefficient and univariate and multivariate analyses were used to assess correlations between parameters. RESULTS: We enrolled 82 patients with 100 UIAs (28 symptomatic and 72 asymptomatic). The median Ktrans (2.1 versus 0.4 min-1; p < 0.001) and WEI (1.5 versus 0.4; p < 0.001) were higher for symptomatic aneurysms than for asymptomatic aneurysms. Ktrans (odds ratio [OR]: 1.60, 95% confidence interval [95% CI]: 1.01-2.52; p = 0.04) and WEI (OR: 3.31, 95% CI: 1.05-10.42; p = 0.04) were independent risk factors for symptomatic aneurysms. Ktrans was positively correlated with WEI (Spearman's coefficient of rank correlation (rs) = 0.41, p < 0.001). The combination of Ktrans and WEI achieved an area under the curve of 0.81 for differentiating symptomatic from asymptomatic aneurysms. CONCLUSIONS: Ktrans may be correlated with symptomatic aneurysms and AWE. Ktrans and WEI may provide an additional value than the PHASES score for risk stratification of UIAs. CLINICAL RELEVANCE STATEMENT: The volume transfer constant (Ktrans) from DCE-MRI perfusion is associated with symptomatic aneurysms and provides additional value above the clinical PHASES score for risk stratification of intracranial aneurysms. KEY POINTS: • The volume transfer constant is correlated with intracranial aneurysm symptoms and aneurysmal wall enhancement. • Dynamic contrast-enhanced and vessel wall MRI facilitates understanding of the pathophysiological characteristics of intracranial aneurysm walls. • The volume transfer constant and wall enhancement index perform better than the traditional PHASES score in differentiating symptomatic aneurysms.

Trends in magnetic resonance and computed tomography angiography utilization among Medicare beneficiaries between 2013 and 2020.

PURPOSE: To evaluate relative and absolute utilization trends and practice patterns in the United States for MRA and CTA. METHODS: Using Medicare Part B physician payment databases (2013-2020), MRA and CTA interpreting physicians and exams were identified using the unique MRA and CTA Healthcare Common Procedure Coding System codes. The number of exams, physicians, demographics, use of contrast, and payments were summarized annually and analyzed to evaluate trends before and during the first year of the COVID-19 pandemic. RESULTS: From 2013 to 2019, the annual number of MRA exams performed decreased by 17.9 %, while the number of CTA exams increased by 90.3 %. The number of physicians interpreting MRA decreased in both hospital (-17.2 %) and outpatient (-7.5 %) environments. The number of physicians interpreting CTA increased in both hospital (+29.4 %) and outpatient (+54.3 %) environments. During the first year of the COVID-19 pandemic, MRA utilization decreased across all imaging environments by 25.0 % whereas CTA only decreased by 5.5 %. Intracranial MRA studies were most often performed without contrast, while contrast use for neck MRA was performed at similar rates as non-contrast exams. CONCLUSION: The overall utilization of MRA and the number of interpreting physicians are decreasing. On the other hand, CTA use and its number of interpreting physicians are increasing. During the first year of the COVID-19 pandemic, use of both MRA and CTA decreased, but the utilization of MRA decreased at five times the rate of CTA.

Serum Interleukin-1 Levels Are Associated with Intracranial Aneurysm Instability.

Serum interleukin-1 (IL-1) are possibly indicative of the inflammation in the intracranial aneurysm (IA) wall. This study aimed to investigate whether IL-1 could discriminate the unstable IAs (ruptured intracranial aneurysms (RIAs) and symptomatic unruptured intracranial aneurysms (UIAs)) from stable, asymptomatic UIAs. IA tissues and blood samples from 35 RIA patients and 35 UIA patients were collected between January 2017 and June 2020 as the derivation cohort. Blood samples from 211 patients with UIAs were collected between January 2021 and June 2022 as the validation cohort (including 63 symptomatic UIAs). Blood samples from 35 non-cerebral-edema meningioma patients (non-inflammatory control) and 19 patients with unknown-cause subarachnoid hemorrhage (hemorrhagic control) were also collected. IL-1ß and IL-1.ra (IL-1 receptor antagonist) were measured in serum and IA tissues, and the IL-1 ratio was calculated as log10 (IL-1.ra/IL-1ß). Based on the derivation cohort, multivariate logistic analysis showed that IL-1ß (odds ratio, 1.48, P = 0.001) and IL-1.ra (odds ratio, 0.74, P = 0.005) were associated with RIAs. The IL-1 ratio showed an excellent diagnostic accuracy for RIAs (c-statistic, 0.91). Histological analysis confirmed the significant correlation of IL-1 between serum and aneurysm tissues. IL-1 ratio could discriminate UIAs from non-inflammatory controls (c-statistic, 0.84), and RIAs from hemorrhagic controls (c-statistic, 0.95). Based on the validation cohort, the combination of IL-1 ratio and PHASES score had better diagnostic accuracy for symptomatic UIAs than PHASES score alone (c-statistic, 0.88 vs 0.80, P < 0.001). Serum IL-1 levels correlate with aneurysm tissue IL-1 levels and unstable aneurysm status, and could serve as a potential biomarker for IA instability.

Evaluating Middle Cerebral Artery Plaque Characteristics and Lenticulostriate Artery Morphology Associated With Subcortical Infarctions at 7T MRI.

BACKGROUND: Lenticulostriate artery (LSA) obstruction is a potential cause of subcortical infarcts. However, MRI LSA evaluation at 3T is challenging. PURPOSE: To investigate middle cerebral artery (MCA) plaque characteristics and LSA morphology associated with subcortical infarctions in LSA territories using 7-T vessel wall MRI (VW-MRI) and time-of-flight MR angiography (TOF-MRA). STUDY TYPE: Prospective. POPULATION: Sixty patients with 80 MCA atherosclerotic plaques (37 culprit and 43 non-culprit). FIELD STRENGTH/SEQUENCE: 7-T with 3D TOF-MRA and T1-weighted 3D sampling perfection with application-optimized contrast using different flip angle evolutions (SPACE) sequences. ASSESSMENT: Plaque distribution (superior, inferior, ventral, or dorsal walls), LSA origin involvement, LSA morphology (numbers of stems, branches, and length), and plaque characteristics (normalized wall index, maximal wall thickness, plaque length, remodeling index, intraplaque hemorrhage, and plaque surface morphology (regular or irregular)) were assessed. STATISTICAL TESTS: Least absolute shrinkage and selection operator regression, generalized estimating equations regression, receiver operating characteristic curve, independent t-test, Mann-Whitney U test, Chi-square test, Fisher's exact test, and intra-class coefficient. A P value <0.05 was considered statistically significant. RESULTS: Plaque irregular surface, superior wall plaque, longer plaque length, LSA origin involvement, fewer LSA stems, and shorter total and average lengths of LSAs were significantly associated with culprit plaques. Multivariable logistic analysis confirmed that LSA origin involvement (OR, 28.51; 95% CI, 6.34-181.02) and plaque irregular surface (OR, 8.32; 95% CI, 1.41-64.73) were independent predictors in differentiating culprit from non-culprit plaques. A combination of LSA origin involvement and plaque irregular surface (area under curve = 0.92; [95% CI, 0.86-0.98]) showed good performance in identifying culprit plaques, with sensitivity and specificity of 86.5% and 86.0%, respectively. DATA CONCLUSION: 7-T VW-MRI and TOF-MRA can demonstrate plaque involvement with LSA origins. MCA plaque characteristics derived from 7-T VW-MRI showed good diagnostic accuracy in determining the occurrence of subcortical infarctions. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 3.

Carotid Plaque-RADS: A Novel Stroke Risk Classification System.

BACKGROUND: Carotid artery atherosclerosis is highly prevalent in the general population and is a well-established risk factor for acute ischemic stroke. Although the morphological characteristics of vulnerable plaques are well recognized, there is a lack of consensus in reporting and interpreting carotid plaque features. OBJECTIVES: The aim of this paper is to establish a consistent and comprehensive approach for imaging and reporting carotid plaque by introducing the Plaque-RADS (Reporting and Data System) score. METHODS: A panel of experts recognized the necessity to develop a classification system for carotid plaque and its defining characteristics. Using a multimodality analysis approach, the Plaque-RADS categories were established through consensus, drawing on existing published reports. RESULTS: The authors present a universal classification that is applicable to both researchers and clinicians. The Plaque-RADS score offers a morphological assessment in addition to the prevailing quantitative parameter of "stenosis." The Plaque-RADS score spans from grade 1 (indicating complete absence of plaque) to grade 4 (representing complicated plaque). Accompanying visual examples are included to facilitate a clear understanding of the Plaque-RADS categories. CONCLUSIONS: Plaque-RADS is a standardized and reliable system of reporting carotid plaque composition and morphology via different imaging modalities, such as ultrasound, computed tomography, and magnetic resonance imaging. This scoring system has the potential to help in the precise identification of patients who may benefit from exclusive medical intervention and those who require alternative treatments, thereby enhancing patient care. A standardized lexicon and structured reporting promise to enhance communication between radiologists, referring clinicians, and scientists.

Gadolinium-enhanced intracranial aneurysm wall imaging and risk of aneurysm growth and rupture: a multicentre longitudinal cohort study.

OBJECTIVES: In patients with an unruptured intracranial aneurysm, gadolinium enhancement of the aneurysm wall is associated with growth and rupture. However, most previous studies did not have a longitudinal design and did not adjust for aneurysm size, which is the main predictor of aneurysm instability and the most important determinant of wall enhancement. We investigated whether aneurysm wall enhancement predicts aneurysm growth and rupture during follow-up and whether the predictive value was independent of aneurysm size. MATERIALS AND METHODS: In this multicentre longitudinal cohort study, individual patient data were obtained from twelve international cohorts. Inclusion criteria were as follows: 18 years or older with ≥ 1 untreated unruptured intracranial aneurysm < 15 mm; gadolinium-enhanced aneurysm wall imaging and MRA at baseline; and MRA or rupture during follow-up. Patients were included between November 2012 and November 2019. We calculated crude hazard ratios with 95%CI of aneurysm wall enhancement for growth (≥ 1 mm increase) or rupture and adjusted for aneurysm size. RESULTS: In 455 patients (mean age (SD), 60 (13) years; 323 (71%) women) with 559 aneurysms, growth or rupture occurred in 13/194 (6.7%) aneurysms with wall enhancement and in 9/365 (2.5%) aneurysms without enhancement (crude hazard ratio 3.1 [95%CI: 1.3-7.4], adjusted hazard ratio 1.4 [95%CI: 0.5-3.7]) with a median follow-up duration of 1.2 years. CONCLUSIONS: Gadolinium enhancement of the aneurysm wall predicts aneurysm growth or rupture during short-term follow-up, but not independent of aneurysm size. CLINICAL RELEVANCE STATEMENT: Gadolinium-enhanced aneurysm wall imaging is not recommended for short-term prediction of growth and rupture, since it appears to have no additional value to conventional predictors. KEY POINTS: • Although aneurysm wall enhancement is associated with aneurysm instability in cross-sectional studies, it remains unknown whether it predicts risk of aneurysm growth or rupture in longitudinal studies. • Gadolinium enhancement of the aneurysm wall predicts aneurysm growth or rupture during short-term follow-up, but not when adjusting for aneurysm size. • While gadolinium-enhanced aneurysm wall imaging is not recommended for short-term prediction of growth and rupture, it may hold potential for aneurysms smaller than 7 mm.

Plaque Evolution and Vessel Wall Remodeling of Intracranial Arteries: A Prospective, Longitudinal Vessel Wall MRI Study.

BACKGROUND: Progression of intracranial atherosclerotic disease (ICAD) is associated with ischemic stroke events and can be quantified with three-dimensional (3D) intracranial vessel wall (IVW) MRI. However, longitudinal 3D IVW studies are limited and ICAD evolution remains relatively unknown. PURPOSE: To evaluate ICAD changes longitudinally and to characterize the imaging patterns of atherosclerotic plaque evolution. STUDY TYPE: Prospective. POPULATION: 37 patients (69 ± 12 years old, 12 females) with angiography confirmed ICAD. FIELD STRENGTH/SEQUENCE: 3.0T/3D time-of-flight gradient echo sequence and T1- and proton density-weighted fast spin echo sequences. ASSESSMENT: Each patient underwent baseline and 1-year follow-up IVW. Then, IVW data from both time points were jointly preprocessed using a multitime point, multicontrast, and multiplanar viewing workflow (known as MOCHA). Lumen and outer wall of plaques were traced and measured, and plaques were then categorized into progression, stable, and regression groups based on changes in plaque wall thickness. Patient demographic and clinical data were collected. Culprit plaques were identified based on cerebral ischemic infarcts. STATISTICAL TESTS: Generalized estimating equations-based linear and logistic regressions were used to assess associations between vascular risk factors, medications, luminal stenosis, IVW plaque imaging features, and longitudinal changes. A two-sided P-value<0.05 was considered statistically significant. RESULTS: Diabetes was significantly associated with ICAD progression, resulting in 6.6% decrease in lumen area and 6.7% increase in wall thickness at 1-year follow-up. After accounting for arterial segments, baseline contrast enhancement predicted plaque progression (odds ratio = 3.61). Culprit plaques experienced an average luminal expansion of 10.9% after 1 year. 74% of the plaques remained stable during follow-up. The regression group (18 plaques) showed significant increase in minimum lumen area (from 7.4 to 8.3 mm2 ), while the progression group (13 plaques) showed significant decrease in minimum lumen area (from 5.4 to 4.3 mm2 ). DATA CONCLUSION: Longitudinal 3D IVW showed ICAD remodeling on the lumen side. Culprit plaques demonstrated longitudinal luminal expansion compared with their non-culprit counterparts. Baseline plaque contrast enhancement and diabetes mellitus were found to be significantly associated with ICAD changes. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 3.

Evaluation of 3-dimensional stereotactic surface projection rendering of arterial spin labeling data in a clinical cohort.

BACKGROUND AND PURPOSE: To assess the feasibility of 3-dimensional stereotactic surface projection (3D-SSP) as applied to arterial spin labeling (ASL) in a clinical pilot study. METHODS: A retrospective sample of 10 consecutive patients who underwent ASL as part of a clinically indicated MR examination was collected during this pilot study. Five additional subjects with normal cerebral perfusion served as a control group. Following voxel-wise M0-correction, cerebral blood flow (CBF) quantification, and stereotactic anatomic standardization, voxel-wise CBF from an individual's ASL dataset was extracted to a set of predefined surface pixels (3D-SSP). A normal database was created from averaging the extracted CBF datasets of the control group. Patients' datasets were compared individually with the normal database by calculating a Z-score on a pixel-by-pixel basis and were displayed in 3D-SSP views for visual inspection. Independent, two-expert reader assessment, using a 3-point scale, compared standard quantitative CBF images to the 3D-SSP maps. RESULTS: Patterns and severities of regionally reduced CBF were identified, by both independent readers, in the 3D-SSP maps. Reader assessment demonstrated preference for 3D-SSP over traditionally displayed standard quantitative CBF images in three of four evaluated imaging metrics (p = .026, .031, and .013, respectively); 3D-SSP maps were never found to be inferior to the standard quantitative CBF images. CONCLUSIONS: Three-dimensional SSP maps are feasible in a clinical population and enable quantitative data extraction and localization of perfusion abnormalities by means of stereotactic coordinates in a condensed display. The proposed method is a promising approach for interpreting cerebrovascular pathophysiology.

Report from the society of magnetic resonance angiography: clinical applications of 7T neurovascular MR in the assessment of intracranial vascular disease.

In recent years, ultra-high-field magnetic resonance imaging (MRI) applications have been rapidly increasing in both clinical research and practice. Indeed, 7-Tesla (7T) MRI allows improved depiction of smaller structures with high signal-to-noise ratio, and, therefore, may improve lesion visualization, diagnostic capabilities, and thus potentially affect treatment decision-making. Incremental evidence emerging from research over the past two decades has provided a promising prospect of 7T magnetic resonance angiography (MRA) in the evaluation of intracranial vasculature. The ultra-high resolution and excellent image quality of 7T MRA allow us to explore detailed morphological and hemodynamic information, detect subtle pathological changes in early stages, and provide new insights allowing for deeper understanding of pathological mechanisms of various cerebrovascular diseases. However, along with the benefits of ultra-high field strength, some challenges and concerns exist. Despite these, ongoing technical developments and clinical oriented research will facilitate the widespread clinical application of 7T MRA in the near future. In this review article, we summarize technical aspects, clinical applications, and recent advances of 7T MRA in the evaluation of intracranial vascular disease. The aim of this review is to provide a clinical perspective for the potential application of 7T MRA for the assessment of intracranial vascular disease, and to explore possible future research directions implementing this technique.

MR Angiography of Extracranial Carotid Disease.

Magnetic resonance angiography sequences, such as time-of-flight and contrast-enhanced angiography, provide clear depiction of vessel lumen, traditionally used to evaluate carotid pathologic conditions such as stenosis, dissection, and occlusion; however, atherosclerotic plaques with a similar degree of stenosis may vary tremendously from a histopathological standpoint. MR vessel wall imaging is a promising noninvasive method to evaluate the content of the vessel wall at high spatial resolution. This is particularly interesting in the case of atherosclerosis as vessel wall imaging can identify higher risk, vulnerable plaques as well as has potential applications in the evaluation of other carotid pathologic conditions.

Unilateral cerebral arterial tortuosity: Associated with aneurysm occurrence, but potentially inversely associated with aneurysm rupture.

PURPOSE: To investigate the association of tortuosity of the main cerebral arteries with intracranial aneurysm (IA) occurrence and rupture. To investigate the relationship between arterial tortuosity and aneurysm morphology as well as conventional risk factors of vascular diseases. METHODS: Three subject groups were analyzed in this study: Patients with ruptured IAs, patients with unruptured IAs, and healthy subjects. The groups were matched by sex and age using tendency score matching. Their intracranial magnetic resonance angiography (MRA) images were collected retrospectively. The intracranial arterial structures were segmented from the MRA images. Arterial tortuosity was measured and statistically compared between the different subject groups and different vessels. Correlation analysis was conducted between arterial tortuosity and clinical risk factors as well as aneurysm morphology. RESULTS: 120 patients were included in the study (average age: 67.5 years; 60% female), 40 for each group after matching. The tortuosity of the aneurysm-bearing artery was significantly greater than that of the contralateral artery in both the ruptured and unruptured IA groups (p < 0.001). There was no significant association between clinical risk factors (history of hypertension, hyperlipidemia, diabetes, smoking, and alcohol use) and arterial tortuosity. There were significant negative correlations between aneurysm-bearing artery tortuosity and aneurysm morphological features such as maximal diameter (p = 0.0011), neck diameter (p < 0.0001), maximum height (p = 0.0024), and size ratio (p = 0.0269). CONCLUSION: The occurrence of cerebral aneurysms correlates to increased unilateral arterial tortuosity, but the risk of aneurysm enlargement/rupturing decreases with greater arterial tortuosity. Abnormal tortuosity may be congenital as tortuosity has no clear connection with acquired common risk factors of vascular diseases.

High-resolution vessel wall magnetic resonance imaging in intracranial vasculopathies: an experience from eastern India.

OBJECTIVE: To evaluate the role of high-resolution intracranial vessel wall imaging (HR-IVWI) in differentiation of various intracranial vasculopathies in addition to luminal and clinical imaging in the largest cohort of Indian stroke patients. METHODS: A single-center, cross-sectional study was undertaken recruiting consecutive stroke or TIA patients presenting within a month of onset, with luminal irregularity/narrowing upstream from the stroke territory. The patients were initially classified into TOAST and Chinese ischemic stroke sub-classification (CISS) on the basis of clinical and luminal characteristics and reclassified again following incorporation of HR-IVWI findings. RESULTS: In our cohort of 150 patients, additional use of HR-IVWI led to a 10.7 and 14% change in initial TOAST and CISS classification respectively (p < 0.001). In TOAST classification, 12 "undetermined aetiology" were reclassified into intracranial atherosclerotic disease (ICAD), 1 "undetermined aetiology" into CNS angiitis and 1 "undetermined aetiology" into arterial dissection. Similarly, in CISS 19 "undetermined aetiology" was reclassified into 16 large artery atherosclerosis (LAA) and 3 "other aetiology" consisting of one CNS angiitis, Moyamoya disease (MMD) and arterial dissection each. Two initial classification of MMD by CISS and TOAST were changed into ICAD. The observed change in diagnosis following incorporation of HR-IVWI was proportionately highest in ICAD (LAA) subgroup (TOAST-9.3%, CISS-12%). CONCLUSION: Adjunctive use of HR-IVWI, to clinical and luminal assessment, can significantly improve diagnostic accuracy during evaluation of intracranial vasculopathies, with its greatest utility in diagnosing in ICAD, CNS angiitis and dissection. ADVANCES IN KNOWLEDGE: HR-IVWI allows clearer etiological distinction of intracranial vasculopathies having therapeutic and prognostic implications.

Co-existing intracranial and extracranial carotid atherosclerosis predicts large-artery atherosclerosis stroke recurrence: a single-center prospective study utilizing combined head-and-neck vessel wall imaging.

OBJECTIVES: Intracranial and extracranial plaque features on high-resolution vessel wall imaging (HR-VWI) are associated with large-artery atherosclerosis (LAA) stroke recurrence. However, most studies have focused on a single vascular bed, and the prognostic value of combined intracranial and extracranial plaque features has yet to be studied. This study aimed to investigate the roles of plaque features, plaque number, and co-existing atherosclerosis in predicting stroke recurrence, utilizing combined head-and-neck HR-VWI. METHODS: From September 2016 to March 2020, participants with acute LAA ischemic strokes were prospectively enrolled and underwent combined head-and-neck HR-VWI. The participants were followed for stroke recurrence for at least 12 months or until a subsequent event occurred. The imaging features at baseline, including conventional and histogram plaque features, plaque number, and co-existing atherosclerosis, were evaluated. Univariable Cox regression analysis and the least absolute shrinkage and selection operator (lasso) method were used for variable screening. Multivariable Cox regression analyses were used to determine the independent risk factors of stroke recurrence. RESULTS: A total of 97 participants (59 ± 12 years, 63 men) were followed for a median of 30.9 months, and 21 participants experienced recurrent strokes. Multivariable Cox analysis identified co-existing intracranial high signal on T1-weighted fat-suppressed images (HST1) and extracranial carotid atherosclerosis (HR, 6.12; 95% CI, 2.52-14.82; p = 0.001) as an independent imaging predictor of stroke recurrence. CONCLUSION: Co-existing intracranial HST1 and extracranial carotid atherosclerosis independently predicted LAA stroke recurrence. Combined head-and-neck HR-VWI is a promising technique for atherosclerosis imaging. CLINICAL RELEVANCE STATEMENT: This prospective study using combined head-and-neck HR-VWI highlighted the necessity of both intracranial culprit plaque evaluation and multi-vascular bed assessment, adding value to the prediction of stroke recurrence. KEY POINTS: • This study highlighted the necessity of both intracranial culprit plaque evaluation and multi-vascular bed assessment, adding value to the prediction of stroke recurrence. • This prospective study using combined head-and-neck HR-VWI found co-existing intracranial HST1 and extracranial carotid atherosclerosis to be independent predictors of stroke recurrence.